NANOSTRUCTURE DYNAMICS IMAGING: Time-resolved electron
tomography provides 3-D views on ultrafast timescale
B
Y INTEGRATING time resolution into a method
the team generated tomographic images and videos that capture a braceletlike carbon nanotube structure wiggling and “breathing” in response to sudden heating pulses. The method, which exploits laserdriven ultrafast electron microscopy technology pioneered by Zewail’s group, provides upclose views of a complex dynamic specimen and promises to have wideranging applications in biological and materials science, the team says. “This is a stunning development in ultrafast time-resolved structural imaging,” says Charles M. Lieber, a chemistry professor at Harvard University. He adds that the Zewail group’s seminal demonstration of time-resolved electron tomography provides researchers with movies of the full 3-D atomic-level structure and dynamics of a nanostructure for the first time. This procedure represents “a remarkable new capability for nanoscience and will also undoubtedly impact substantially the life sciences,” he says. Rice University chemistry professor James L. Kinsey is equally enthusiastic about the new imaging technique. “This work is an impressive extension of technology for studying structural change in nanoscale objects,” he says. “It would be hard to predict the impact of this advance on molecular science, but it is sure to be profound.”—MITCH JACOBY
that generates three-dimensional electron microscopy images, researchers in California have developed a technique that provides a 3-D view of nanometer-scale specimens moving on the femtosecond timescale (Science 2010, 328, 1668). The procedure, dubbed 4-D electron tomography, offers a novel way to probe the dynamics of microscopic objects undergoing subtle transient motions and structural changes. Conventional transmission electron micrographs are 2-D projections of 3-D specimens. By recording many 2-D projections at various viewing angles, which can be carried out by tilting the specimen incrementally and recording an image at each tilt angle, a 3-D composite image can be constructed with the help of computer algorithms. This well-established electron tomography procedure can provide researchers with detailed 3-D views of complex specimens from multiple perspectives. Although this type of analysis readily leads to geometric and structural insights that cannot be derived from flat projections alone, the information obtained in this way paints a time-averaged picture of a static object in an equilibrium state. Now, such high-resolution electron tomography has taken on a new dimension: time. California Institute of Technology senior postdoc Oh-Hoon Kwon and chemistry Nobel Laureate Ahmed H. Zewail have developed a way to produce tomograms with nanoscale spatial resolution and femtosecond temporal resolution. To watch the nanotube structure move, click on this MORE ONLINE In a demonstration study, story at www.cen-online.org.
AHMED ZEWAIL/CALTECH
NEWS OF THE WEEK
A 4-D electron tomography method provides a 3-D view of this carbon nanotube spiral (orange and yellow), shown here against an artistic background, as it wiggles and moves. The braceletlike structure has a radius of about 620 nm.
INVESTIGATION Chemical safety board will probe BP/Deepwater Horizon rig explosion At the request of Congress, the Chemical Safety & Hazard Investigation Board (CSB) will investigate the causes of the April 20 explosion on the BP/Deepwater Horizon drilling rig in the Gulf of Mexico. The board “intends to proceed with an investigation of the root causes of the accidental chemical release that destroyed the Deepwater Horizon rig and took the lives of 11 workers,” CSB Chairman John S. Bresland told House Energy & Commerce Committee Chairman Henry A. Waxman (D-Calif.) in a June 18 letter.
Earlier this month, Waxman asked CSB to examine whether the circumstances and events leading up to the accident reflect problems in BP’s corporate safety culture. He also asked the board to determine whether any parallels exist between the oil rig explosion and the 2005 explosion at BP’s Texas City, Texas, refinery that killed 15 workers (C&EN, June 14, page 35). Bresland pledged that CSB will approach the inquiry “without any preconceptions” and conduct a thorough and objective examination of “all possible
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underlying factors and causes.” The board plans to focus only on events leading up to and including the explosion. An examination of the response to the disaster and of the impact of the massive oil spill is “beyond” CSB’s resources and abilities, Bresland noted. Including the Deepwater Horizon accident, CSB currently has a record-high 21 ongoing investigations. BP is cooperating with all government investigations, a company spokesman says.—GLENN HESS
